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Active optical antennaRelated Patent Categories: Coherent Light Generators, Particular Active Media, SemiconductorActive optical antenna description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070058686, Active optical antenna. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS-REFERENCE TO RELATED APPLICATIONS [0001] The present application claims the benefit of the filing dates of U.S. Provisional Application Ser. No. 60/708,659 entitled "Active Optical Antennas" and filed on Aug. 16, 2005 and U.S. Provisional Application Ser. No. 60/753,704 entitled "Active Optical Antenna" and filed on Dec. 24, 2005. [0002] The above cross-referenced related applications are hereby incorporated by reference herein in their entirety. STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT [0003] None. BACKGROUND OF THE INVENTION [0004] 1. Field Of The Invention [0005] The present invention relates to a new class of photonic devices referred to as active optical antennas and instrumentation incorporating such devices. [0006] 2. Brief Description Of The Related Art [0007] To achieve below diffraction limit resolution, the Near Field Scanning Optical Microscope, which uses subwavelength apertures in metals, has become a tool of choice to produce optical spots of nanometric dimensions (See E. Betzig and J. K. Trautman, Science 257, 189 (1992)). This technique suffers however from limited optical throughput, which limits the range of applications. This problem has been partially alleviated through the use of so called solid immersion lenses (See M. Mansfield and G. S. Kino, Appl. Phys. Lett. 57, pp. 2615 (1990) and K. B. Crozier et al, Journal of Microelectromechanical Systems 11, pp. 470 (2002)) [0008] An alternative approach is to scatter instead the incident light with a so-called optical antenna of subwavelength dimensions, which enhances the near field intensity by many orders of magnitude compared to NSOMs (See K. B. Crozier et al, Journal of Applied Physics 94, pp. 4632 (2003)) Physically in an optical antenna the incident light is coupled into surface plasmon (SP) modes. These are surface optical waves coupled to collective charge oscillations in the metal, known as plasmons. The SPs have wavelengths well below that of light in free space due to their large effective refractive index. As a result light gets concentrated and is re-radiated into the near field down to dimensions in the 10-100 nm range. [0009] Surface plasmons are collective excitations of the electron plasma in a metal by electromagnetic radiation. (See S. A. Maier and H. Atwater, J. Appl. Phys. 98, 1 (2005) and A. V. Zayats, I. I. Smolyaninov, A. A. Maradudin, Physics Rep. 408, 131 (2005)) They have been extensively used in various applications ranging from biosensors to near field optical microscopes and devices. Early applications such as surface plasmon microscopy such as is described in B. Rothenhausler and W. Knoll, Nature 332, 615 (1988), some of which have achieved single atomic layer sensitivity (see A. N. Grigorenko, P. I. Nikitin, and A. V. Kabashin, Appl. Phys. Lett. 75, 3917 (1999), made use of plasmon excitation in thin metal films. [0010] With the currently available nanofabrication techniques such as electron beam lithography and focused ion beam (FIB) milling, it has become possible to exploit plasmon resonances in coupled metallic nanoparticles, including periodic arrays. Experiments have demonstrated a large optical near-field enhancement around such nanoparticles, which is important for surface spectroscopic techniques such as surface enhanced Raman spectroscopy (SERS). (See S. Nie and S. R. Emory, Science 275, 1102 (1997)). [0011] Optical antennas are single or coupled metallic nanoparticles in which optical excitation of surface plasmons can produce very high intensities in the optical near field due to the high curvature of the metal surfaces. The field enhancement relative to the incident field is maximum when the wavelength is suitably matched to the size of the nanoparticle (resonant optical antenna). Optical antennas were first demonstrated at microwave frequencies and more recently at mid-infrared and near infrared frequencies (See P. J. Schuck, D. P. Fromm, A. Sundaramurthy, G. S. Kino, and W. E. Moemer, Phys. Rev. Lett. 94, 017402 (2005); P. Muhlschlegel, H. J. Eisler, O. J. F. Martin, B. Hecht, and D. W. Pohl, Science 308, 1607 (2005); and J. N. Farahani, D. W. Pohl, H. J. Eisler, and B. Hecht, Phys. Rev. Lett. 95, 017402 (2005). Of particular interest are resonant optical antennas comprising a pair of strongly coupled metallic nanorods. This design leads to a large intensity enhancement localized in the gap between the latter. [0012] U.S. Patent Publication No. US2001/0009541, published on Jul. 26, 2001, discloses a system in which "a laser beam emitted from a semiconductor laser enters an incident surface of a transparent condensing medium with a central part of the laser beam being shielded by a shading metal member, and a light spot is formed on a light-condensed surface of the transparent condensing medium. When this light spot is applied to a micro metal member, plasmon of the micro metal member is excited, and near field light leaks out there from. The near field light enters a recording medium of a disk as propagation light, and recording into and reproduction from the recording medium is performed by this light." [0013] The enhanced transmission of light through sub-wavelength apertures and aperture arrays in metal films, a phenomenon associated with surface plasmons, has also attracted considerable interest. (See T. W. Ebbesen, H. J. Lezec, H. F. Ghaemi, T. Thio, and P. A. Wolff, Nature 391, 667 (1998)). Very small aperture lasers that consist of a laser diode with its facet coated by a metal film on which a sub-wavelength aperture such as a circular hole or a C-aperture is etched by FIB milling, have been demonstrated. (See A. Partovi, D. Peale, M. Wuttig, C. A. Murray, G. Zydzik, L. Hopkins, K. Baldwin, W. S. Hobson, J. Wynn, J. Lopata, L. Dhar, R. Chichester, and J. H. Yeh, Appl. Phys. Lett. 75, 1515 (1999); F. Chen, A. Itagi, J. A. Bain, D. D. Stancil, T. E. Schlesinger, L. Stebounova, G. C. Walker, and B. B. Akhremitchev, Appl. Phys. Lett. 83, 3245 (2003); and U.S. Patent Publication No. US2005/0030993 A1). However, these devices suffer from limited output power even though the transmission is enhanced when normalized to the aperture area. SUMMARY OF THE INVENTION [0014] A new class of photonic devices called active optical antennas, which consist of metallic structures directly integrated onto the facet of a semiconductor laser, and of instruments based on such antennas is disclosed. The structures consist of metallic elements which function as antennas at optical wavelengths by spatially concentrating laser radiation of wavelength in the range from the UV to the mid-infrared into spots (with sizes in the range 10-100 nm) in the so called near field zone, that is at subwavelength distances from the facet. Various antenna designs are considered depending on the laser under consideration and applications. [0015] This invention has wide ranging applications such as new microscopes for high-resolution spatially resolved imaging and spectroscopy, new probes for biology, laser assisted processing and repair of devices, circuits and masks, as well new optical tweezers and phased array devices. Microscopes and other systems based on this invention are discussed. [0016] In a preferred embodiment, the present invention is a semiconductor laser apparatus that comprises an active region, a laser facet and an optical antenna on said laser facet. The optical antenna may take any of a number of forms, including but not limited to a bow tie antenna, a dipolar optical antenna, and a cross optical antenna. The active optical antenna further could be formed in an opening in a metal coating on the facet of the laser. The semiconductor laser could, for example, be a diode laser or a quantum cascade laser. [0017] In another preferred embodiment, the present invention is a semiconductor laser apparatus that comprises an active region, a facet and a metallic structure integrated on the facet of the semiconductor laser. The metallic structure may comprise metallic elements functioning as antennas at optical wavelengths by spatially concentrating laser radiation of wavelength in the near field zone. [0018] In still another embodiment, the present invention is a laser apparatus that comprises a laser, an optical fiber coupled to the laser where the optical fiber has a facet and an optical antenna is formed on the facet of the optical fiber. The optical antenna may comprise, for example, an array of metallic nanorods, a bow tie antenna, a cross optical antenna, or a dipolar optical antenna. The optical antenna also may comprise a metal coating having an opening therein or may comprise an array of optical antennas. [0019] In yet another embodiment, the present invention is a laser apparatus that comprises a fiber laser having a facet and an optical antenna on said facet of said fiber laser. In still other embodiments, the present invention is an instrument such as an optical storage device, an NSOM for imaging or chemical analysis, a mask, or a device for IC repair. [0020] In another embodiment, the present invention is a laser apparatus that comprises a fiber laser amplifier having a facet and an optical antenna on the facet. The optical antenna may comprise an array of optical antennas. Continue reading about Active optical antenna... Full patent description for Active optical antenna Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Active optical antenna patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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